Pfizer Halts Dosing in Late-Stage DMD Study Following Death of Young Patient

Pictured: Entrance to Pfizer's office in Brussels,

Pictured: Entrance to Pfizer’s office in Brussels,

Alexandros Michailidis/Getty Images

Pfizer’s investigational Duchenne muscular dystrophy gene therapy fordadistrogene movaparvovec has been hit with another patient death, forcing the pharma to pause dosing in its Phase III study.

Pictured: Entrance to Pfizer’s office in Belgium/iStock, Alexandros Michailidis

Pfizer on Tuesday announced that a patient died in the Phase II DAYLIGHT study, evaluating its investigational gene therapy fordadistrogene movaparvovec in Duchenne muscular dystrophy.

The patient has “passed away suddenly,” the pharma noted in a letter shared by nonprofit patient group Parent Project Muscular Dystrophy on Tuesday. Pfizer still does not have complete information regarding the incident and is currently working with the trial’s investigator to better understand the mortality.

The patient death has affected Pfizer’s Phase III CIFFREO cross-over trial in Duchenne muscular dystrophy (DMD). According to the company, it completed initial dosing for CIFFREO in 2023 but has decided to suspend the administration of fordadistrogene movaparvovec for the study’s cross-over portion. The trial will continue otherwise as scheduled.

“The safety and well-being of the patients in our clinical trials remains our top priority,” Pfizer wrote in its letter, noting that it will work with regulatory authorities and an independent external data monitoring committee to assess the incident. The company will share more information with the broader medical and patient community “as soon as we can.”

“On behalf of everyone at Pfizer, we extend our sympathies to his family, friends, and those closest to his care,” the pharma wrote in its letter.

Tuesday’s announcement follows a previous patient death in a fordadistrogene movaparvovec study. In December 2021, Pfizer was also forced to pause screening and dosing in a Phase Ib DMD study after an unexpected patient death. At the time, the pharma did not specify whether the patient had been treated with the investigational gene therapy before the death.

In April 2022, the FDA lifted its clinical hold on the Investigational New Drug application for fordadistrogene movaparvovec, allowing Pfizer to open the first U.S. sites for CIFFREO.

DMD is a severe and genetic disease characterized by the progressive degeneration of muscles, leading to weakness and difficulty moving. It eventually affects vital organs such as the lungs, which could ultimately result in respiratory failure.

The disease mainly affects young boys between the ages of two and three years of age and is is caused by mutations to the gene encoding for the dystrophin protein, which is crucial for muscle function and stability. Pfizer’s fordadistrogene movaparvovec works by delivering a functional but shortened version of the dystrophin gene. The gene therapy uses an AAV9 capsid as its delivery mechanism, which is known to be able to target muscle tissue.

Tristan Manalac is an independent science writer based in Metro Manila, Philippines. Reach out to him on LinkedIn or email him at tristan@tristanmanalac.com or tristan.manalac@biospace.com.

Tristan is an independent science writer based in Metro Manila, with more than eight years of experience writing about medicine, biotech and science. He can be reached at tristan.manalac@biospace.com, tristan@tristanmanalac.com or on LinkedIn.
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